i don't know if i'm right but souls of purgatory are like カートリッジ for God-castiel...but this weopons gonna empty after god-cass'll killing all his enemies in heaven?

maybe i misunderstood...but it seemed that castiel needed souls to arm his weapon and killed raphael...so each time he killed または gonna kill someone he ロスト cartrigde, his weapon will ended to be empty?...am i right または wrong? am i misunderstood something in the explanations of 6th season?